JPH0671000B2 - Wiring formation method for semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wiring forming method for a semiconductor device, and more particularly to a multilayer wiring forming method using a refractory metal such as molybdenum (Mo) or tungsten (W). Is.

SUMMARY OF THE INVENTION The present invention is directed to the formation of a wiring layer made of a refractory metal such as Mo or W, etching the metal oxide film on the surface thereof, and then covering the wiring layer in a non-oxidizing atmosphere. The growth of the insulating film improves the adhesion between the wiring layer and the insulating film and enables reliable electrical connection to the wiring layer.

[Conventional technology]

Conventionally, it has been known to form fine wiring such as LSI using a refractory metal such as Mo or W.

As a method for forming such fine wiring, after depositing a refractory metal, patterning is performed by dry etching such as plasma etching using the photoresist layer as a mask, and then the photoresist film is etched (ashed) in oxygen plasma. Removed and then on the patterned metal layer
The interlayer insulating film such as SiO ₂ is formed under normal pressure CVD (chemical paper,
A deposition method has been proposed.

[Problems to be solved by the invention]

According to the above-mentioned conventional method, there are the following problems (a) and (b).

(A) Adhesion between the metal layer and the insulating film is poor, and when another wiring metal is deposited on the insulating film by vapor deposition or sputtering and heat-treated, the insulating film may peel off from the sea surface of the metal layer below. occured.

(B) After forming a contact hole in the insulating film, another wiring metal was deposited to electrically connect the upper and lower metal layers, but there were many cases of poor connection.

The cause of these problems was investigated, and it was found that the metal oxide film was formed on the surface of the refractory metal layer at the time of assuring the photoresist layer and preheating (about 350 to 500 ° C) before film growth by the atmospheric pressure CVD device. It was discovered that

[Means for solving problems]

The present invention has been made to solve the above-mentioned problems and is characterized in that the metal oxide film is removed from the surface of the refractory metal layer and the insulating film is vapor-phase grown in a non-oxidizing atmosphere. It is what

That is, the wiring forming method of the semiconductor device according to the present invention is
It includes the following steps (a) to (c).

(a) A wiring layer made of a refractory metal such as Mo or W is formed on the first insulating film such as SiO ₂ covering the surface of the semiconductor substrate.

(b) The metal oxide film on the surface of the wiring layer is removed by etching.

(c) After removing the metal oxide film, a second layer of SiO ₂ , Si ₃ N _4, etc. is formed in a non-oxidizing atmosphere (eg, under reduced pressure, Ar gas, etc.) so as to cover the wiring layer and the first insulating film. Vapor growth of the insulating film. In this case, a low pressure CVD method, a plasma CVD method or the like can be used.

[Action]

According to the method of the present invention described above, the metal oxide film is removed and the second insulating film is vapor-phase grown in a non-oxidizing atmosphere. Therefore, the metal oxide film is formed between the wiring layer and the second insulating film. There is no intervening film, and good adhesion can be obtained between the wiring layer and the insulating film. Therefore, even if another metal layer for wiring is deposited on the second insulating film and then heat-treated, it is possible to prevent a situation in which the second insulating film is peeled off from the metal bath thereunder.

In addition, even when a metal layer for wiring is deposited to electrically connect the upper and lower metal layers after providing the contact hole in the second insulating film, it is preferable that the upper and lower metal layers be connected to each other. A reliable ohmic contact is obtained.

〔Example〕

FIGS. 1 to 4 show steps of a method for forming a multilayer wiring according to an embodiment of the present invention, and steps (1) to (d) corresponding to respective drawing numbers will be sequentially described.

(1) SiO _{2 on} the surface of a semiconductor substrate 10 made of, for example, silicon
After forming the first insulating film 12 made of
A refractory metal such as Mo or W is deposited on the above by a vacuum vapor deposition method, a sputtering method or the like, and patterning is performed according to a predetermined wiring pattern to form a first wiring layer 14. In this case, in patterning, dry etching such as plasma etching is performed using the photoresist layer 16 as a mask, and then the photoresist layer 16 is removed by ashing in oxygen plasma. At the time of this assembling, a metal oxide film 18 is formed on the surface of the wiring layer 14.

(2) Next, the metal oxide film 18 on the surface of the wiring layer 14 is etched away using an appropriate etching liquid. This may be done just before the next CVD process.

(3) Second insulating film 2 so as to cover the wiring layer 14 and the insulating film 12
0 is vapor-deposited under reduced pressure (for example, 0.1 to 10 Torr).
That is, as an example, the insulating film 20 is formed by depositing SiO ₂ , Si ₃ N _4, etc. by the low pressure CVD method. Conventionally, normal pressure
Although the insulating film 20 was formed by the CVD method, the metal oxide film was formed on the surface of the wiring layer 14 in the preheating step as described above. However, as described above, when the insulating film 20 is formed by the low pressure CVD method, since preheating is not performed in an oxidizing atmosphere before the CVD film growth, a metal oxide film is not generated, The insulating film 20 comes into close contact with the wiring layer 14.

(4) After forming a contact hole in the insulating film 20 so that a part of the wiring layer 14 is exposed, a wiring metal such as Al is deposited on the upper surface of the substrate by a vacuum deposition method, a sputtering method, or the like and appropriately patterned. As a result, the second wiring layer 22 is formed. As described above, since there is no metal oxide film on the surface of the wiring layer 14, the wiring layer 22 reliably and satisfactorily makes ohmic contact with the wiring layer 14.

〔The invention's effect〕

As described above, according to the present invention, after forming a wiring layer made of a refractory metal such as Mo or W which is easily oxidized, the metal oxide film on the surface of the wiring layer is removed by etching and then an insulating film is formed thereon. Since the vapor phase growth is performed in a non-oxidizing atmosphere, the metal oxide film is not present between the wiring layer and the insulating film, the adhesion between the two is greatly improved, and the reliability of the wiring layer is improved. The effect that electrical connection is possible is obtained.

[Brief description of drawings]

1 to 4 are cross-sectional views of a substrate showing a multilayer wiring forming process according to an embodiment of the present invention. 10: semiconductor substrate, 12: first insulating film, 14: first wiring layer, 20: second insulating film, 22: second wiring layer.

Claims (1)

[Claims] 1. A step of: (a) forming a wiring layer made of a refractory metal on a first insulating film covering a surface of a semiconductor substrate; and (b) etching the surface of the wiring layer to form a metal oxide film. And (c) after removing the metal oxide film, vapor-growing a second insulating film in a non-oxidizing atmosphere so as to cover the wiring layer and the first insulating film. Forming method of semiconductor device including: